[re.req]

In Table 135 X denotes a traits class defining types and functions for the character container type charT; u is an object of type X; v is an object of type const X; p is a value of type const charT*; I1 and I2 are input iterators; F1 and F2 are forward iterators; c is a value of type const charT; s is an object of type X::string_type; cs is an object of type const X::string_type; b is a value of type bool; I is a value of type int; cl is an object of type X::char_class_type, and loc is an object of type X::locale_type.

Table 135: Regular expression traits class requirements [tab:re.req]

🔗	Expression	Return type	Assertion/note pre-/post-condition
🔗	X::char_type	charT	The character container type used in the implementation of class template basic_regex.
🔗	X::string_type	basic_string<charT>
🔗	X::locale_type	A copy constructible type	A type that represents the locale used by the traits class.
🔗	X::char_class_type	A bitmask type .	A bitmask type representing a particular character classification.
🔗	X::length(p)	size_t	Yields the smallest i such that p[i] == 0. Complexity is linear in i.
🔗	v.translate(c)	X::char_type	Returns a character such that for any character d that is to be considered equivalent to c then v.translate(c) == v.translate(d).
🔗	v.translate_nocase(c)	X::char_type	For all characters C that are to be considered equivalent to c when comparisons are to be performed without regard to case, then v.translate_nocase(c) == v.translate_nocase(C).
🔗	v.transform(F1, F2)	X::string_type	Returns a sort key for the character sequence designated by the iterator range [F1, F2) such that if the character sequence [G1, G2) sorts before the character sequence [H1, H2) then v.transform(G1, G2) < v.transform(H1, H2).
🔗	v.transform_primary(F1, F2)	X::string_type	Returns a sort key for the character sequence designated by the iterator range [F1, F2) such that if the character sequence [G1, G2) sorts before the character sequence [H1, H2) when character case is not considered then v.transform_primary(G1, G2) < v.transform_primary(H1, H2).
🔗	v.lookup_collatename(F1, F2)	X::string_type	Returns a sequence of characters that represents the collating element consisting of the character sequence designated by the iterator range [F1, F2). Returns an empty string if the character sequence is not a valid collating element.
🔗	v.lookup_classname(F1, F2, b)	X::char_class_type	Converts the character sequence designated by the iterator range [F1, F2) into a value of a bitmask type that can subsequently be passed to isctype. Values returned from lookup_classname can be bitwise OR'ed together; the resulting value represents membership in either of the corresponding character classes. If b is true, the returned bitmask is suitable for matching characters without regard to their case. Returns 0 if the character sequence is not the name of a character class recognized by X. The value returned shall be independent of the case of the characters in the sequence.
🔗	v.isctype(c, cl)	bool	Returns true if character c is a member of one of the character classes designated by cl, false otherwise.
🔗	v.value(c, I)	int	Returns the value represented by the digit c in base I if the character c is a valid digit in base I; otherwise returns -1. [Note 2: The value of I will only be 8, 10, or 16. — end note]
🔗	u.imbue(loc)	X::locale_type	Imbues u with the locale loc and returns the previous locale used by u if any.
🔗	v.getloc()	X::locale_type	Returns the current locale used by v, if any.

30 Regular expressions library [re]

30.2 Requirements [re.req]